Photonic integration enabling new multiplexing concepts in optical board-to-board and rack-to-rack interconnects

New broadband applications are causing the datacenters to proliferate, raising the bar for higher interconnection speeds. So far, optical board-to-board and rack-to-rack interconnects relied primarily on low-cost commodity optical components assembled in a single package. Although this concept proved successful in the first generations of optical-interconnect modules, scalability is a daunting issue as signaling rates extend beyond 25 Gb/s. In this paper we present our work towards the development of two technology platforms for migration beyond Infiniband enhanced data rate (EDR), introducing new concepts in board-to-board and rack-to-rack interconnects. The first platform is developed in the framework of MIRAGE European project and relies on proven VCSEL technology, exploiting the inherent cost, yield, reliability and power consumption advantages of VCSELs. Wavelength multiplexing, PAM-4 modulation and multi-core fiber (MCF) multiplexing are introduced by combining VCSELs with integrated Si and glass photonics as well as BiCMOS electronics. An in-plane MCF-to-SOI interface is demonstrated, allowing coupling from the MCF cores to 340x400 nm Si waveguides. Development of a low-power VCSEL driver with integrated feed-forward equalizer is reported, allowing PAM-4 modulation of a bandwidth-limited VCSEL beyond 25 Gbaud. The second platform, developed within the frames of the European project PHOXTROT, considers the use of modulation formats of increased complexity in the context of optical interconnects. Powered by the evolution of DSP technology and towards an integration path between inter and intra datacenter traffic, this platform investigates optical interconnection system concepts capable to support 16QAM 40GBd data traffic, exploiting the advancements of silicon and polymer technologies

FirstLight: Pluggable Optical Interconnect Technologies for Polymeric Electro-Optical Printed Circuit Boards in Data Centers

The protocol data rate governing data storage devices will increase to over 12 Gb/s by 2013 thereby imposing unmanageable cost and performance burdens on future digital data storage systems. The resulting performance bottleneck can be substantially reduced by conveying high-speed data optically instead of electronically. A novel active pluggable 82.5 Gb/s aggregate bit rate optical connector technology, the design and fabrication of a compact electro-optical printed circuit board to meet exacting specifications, and a method for low cost, high precision, passive optical assembly are presented. A demonstration platform was constructed to assess the viability of embedded electro-optical midplane technology in such systems including the first ever demonstration of a pluggable active optical waveguide printed circuit board connector. High-speed optical data transfer at 10.3125 Gb/s was demonstrated through a complex polymer waveguide interconnect layer embedded into a 262 mm × 240 mm × 4.3 mm electro-optical midplane. Bit error rates of less than 10-12 and optical losses as low as 6 dB were demonstrated through nine multimode polymer wave guides with an aggregate data bandwidth of 92.8125 Gb/s

A Multi-Floor Arrayed Waveguide Grating Based Architecture with Grid Topology for Datacenter Networks

This paper proposes a grid topology based passive optical interconnect (POI) architecture that is composed of multiple floors of arrayed waveguide grating routers (AWGRs) to offer high connectivity and scalability for datacenter networks. In the proposed POI signal only needs to pass one AWGR, and thus can avoid the crosstalk accumulation and cascaded filtering effects, which exist in many existing POI architectures based on cascaded AWGRs. Meanwhile, due to high connectivity, the proposed grid topology based POI also has the potential advantage of high reliability. Simulation results validate the network performance. With a proper node degree, the proposed grid topology can achieve acceptable blocking probability. Besides, steady performance is kept when the number of floors increases, indicating good scalability of the proposed POI

To overcome the scalability limitation of passive optical interconnects in datacentres

We propose to add optical amplifier(s) to passive optical interconnect (POI) at top-of-rack in datacentres and validate this approach by introducing impairment constraints into POIs design. It is shown that one amplifier can improve scalability by a factor of 16

Evolution of system embedded optical interconnect in sub-top of rack data center systems

This research was funded by the EU FP7 project “PhoxTrot”, for which it has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement No. 318240, the Horizon2020 Nephele project (Grant No. 645212), the Horizon2020 COSMICC project (Grant No. 688516).In this paper we review key technological milestones in system embedded optical interconnects in data centers that have been achieved between 2014 and 2020 on major European Union research and development projects. This includes the development of proprietary optically enabled data storage and switch systems and optically enabled data storage and compute subsystems. We report on four optically enabled data center system demonstrators: LightningValley, ThunderValley2, Pegasus and Aurora, which include advanced optical circuits based on polymer waveguides and fibers and proprietary electro-optical connectors. We also report on optically enabled subsystems including Ethernet-connected hard disk drives and microservers. Both are designed in the same pluggable carrier form factor and with embedded optical transceiver and connector interfaces, thus allowing, for the first time, both compute and storage nodes to be optically interchangeable and directly interconnectable over long distances. Finally, we present the Nexus platform, which allows different optically enabled data center test systems and subsystems to be interconnected and comparatively characterized within a data center test environment.Publisher PDFPeer reviewe

Optical Networks and Interconnects

The rapid evolution of communication technologies such as 5G and beyond, rely on optical networks to support the challenging and ambitious requirements that include both capacity and reliability. This chapter begins by giving an overview of the evolution of optical access networks, focusing on Passive Optical Networks (PONs). The development of the different PON standards and requirements aiming at longer reach, higher client count and delivered bandwidth are presented. PON virtualization is also introduced as the flexibility enabler. Triggered by the increase of bandwidth supported by access and aggregation network segments, core networks have also evolved, as presented in the second part of the chapter. Scaling the physical infrastructure requires high investment and hence, operators are considering alternatives to optimize the use of the existing capacity. This chapter introduces different planning problems such as Routing and Spectrum Assignment problems, placement problems for regenerators and wavelength converters, and how to offer resilience to different failures. An overview of control and management is also provided. Moreover, motivated by the increasing importance of data storage and data processing, this chapter also addresses different aspects of optical data center interconnects. Data centers have become critical infrastructure to operate any service. They are also forced to take advantage of optical technology in order to keep up with the growing capacity demand and power consumption. This chapter gives an overview of different optical data center network architectures as well as some expected directions to improve the resource utilization and increase the network capacity

A Hybrid Beam Steering Free-Space and Fiber Based Optical Data Center Network

Wireless data center networks (DCNs) are promising solutions to mitigate the cabling complexity in traditional wired DCNs and potentially reduce the end-to-end latency with faster propagation speed in free space. Yet, physical architectures in wireless DCNs must be carefully designed regarding wireless link blockage, obstacle bypassing, path loss, interference and spatial efficiency in a dense deployment. This paper presents the physical layer design of a hybrid FSO/in-fiber DCN while guaranteeing an all-optical, single hop, non-oversubscribed and full-bisection bandwidth network. We propose two layouts and analyze their scalability: (1) A static network utilizing only tunable sources which can scale up to 43 racks, 15,609 nodes and 15,609 channels; and (2) a re-configurable network with both tunable sources and piezoelectric actuator (PZT) based beam-steering which can scale up to 8 racks, 2,904 nodes and 185,856 channels at millisecond PZT switching time. Based on a traffic generation framework and a dynamic wavelength-timeslot scheduling algorithm, the system-level network performance is simulated for a 363-node subnet, reaching >99% throughput and 1.23 μ s average scheduler latency at 90% load

FirstLight: Pluggable Optical Interconnect Technologies for Polymeric Electro-Optical Printed Circuit Boards in Data Centers

The protocol data rate governing data storage devices will increase to over 12 Gb/s by 2013 thereby imposing unmanageable cost and performance burdens on future digital data storage systems. The resulting performance bottleneck can be substantially reduced by conveying high-speed data optically instead of electronically. A novel active pluggable 82.5 Gb/s aggregate bit rate optical connector technology, the design and fabrication of a compact electro-optical printed circuit board to meet exacting specifications, and a method for low cost, high precision, passive optical assembly are presented. A demonstration platform was constructed to assess the viability of embedded electro-optical midplane technology in such systems including the first ever demonstration of a pluggable active optical waveguide printed circuit board connector. High-speed optical data transfer at 10.3125 Gb/s was demonstrated through a complex polymer waveguide interconnect layer embedded into a 262 mm × 240 mm × 4.3 mm electro-optical midplane. Bit error rates of less than 10-12 and optical losses as low as 6 dB were demonstrated through nine multimode polymer wave guides with an aggregate data bandwidth of 92.8125 Gb/s